The invention relates to a ring laser provided with a ring of semiconductor material for generating laser radiation, a coupler for coupling radiation out of the ring, two waveguides connected to the coupler, a combiner, two inputs of which are connected to the waveguides, and an output waveguide connected to an output of the combiner.
A ring laser of this type is known from the article "Very low threshold current operation of semiconductor ring lasers", IEEE Proceedings-J, vol. 139, no. 6, Dec. 1992 by T. Kraus and P. J. R. Laybourn. In the known semiconductor ring laser, radiation of two waves travelling in opposite directions in the ring are coupled into two waveguides by means of two Y junctions. The radiation in the two waveguides is combined in an output waveguide by means of an Y junction. A drawback of this ring laser is that it has a relatively low efficiency, i.e. the supplied optical power is low at a given electric input power.